【作者】 陈勇；

【导师】 陈戈；

【作者基本信息】 中国海洋大学 ， 地图学与地理信息系统， 2007， 博士

【摘要】 三维虚拟城市是数字城市的重要组成部分,其研究内容涉及虚拟现实、实时仿真、路径规划以及交互等许多重要的底层支撑技术,也是地图学与地理信息系统的一个前沿性研究课题。本文对三维虚拟城市构建中的关键技术进行了研究,着重讨论了海量山地地形的绘制、大规模场景实时漫游系统的设计与开发、三维场景中漫游的路径规划技术、海滨城市场景中的近岸海浪仿真四个方面的关键技术:1.海量地形的实时绘制讨论了海量山地地形绘制的相关研究。提出了一个基于金字塔结构组织的海量地形几何和纹理数据组织与调度的方法,对原始数据进行预处理:分层和分块,在绘制时根据视锥选择可见的数据块读入内存,根据视点的位置方位和层次法向锥选择相应的分辨率层次,实现了海量地形数据的实时绘制。2.大规模场景实时漫游系统讨论了大规模场景实时漫游系统,研究场景绘制中的绘制加速技术、场景组织与管理、快速消隐和碰撞检测等相关技术,最后以虚拟校园为例,用VC和OPENGL编程,尝试着将虚拟现实技术、多媒体技术和地理信息系统有机地结合起来,实现了大规模场景实时漫游系统。3.三维场景漫游中的路径规划技术。讨论了路径规划技术的相关研究。对地理信息系统GIS和机器人学领域的路径规划方法进行分析,根据三维场景中漫游的特点,提出了一种新型、快速的三维场景中漫游的自动路径规划算法:橡皮筋算法,首先基于场景投影矩阵,生成基本路径,再用橡皮筋算法优化,最后可得到最优路径。该算法在解决复杂场景避障、大片可行走区域等问题上具有明显优势。4.近岸海浪仿真讨论了海浪仿真技术的相关研究,针对近岸海浪仿真的困难性和海滨城市虚拟场景的需求,提出了一种近岸海浪实时仿真方法。采用椭圆余弦波来构造波形,解决了近岸海浪绘制中的波浪卷曲变形,采用波向线和波峰线组成的变形网络,实现了近岸海浪的折射模拟,并提出了一种适用于视觉仿真的快速波向线和波峰线生成算法,成功的实现了近岸海浪实时仿真。更多还原

【Abstract】 Three-dimensional virtual city is an important component of digital city. It involves many substrate supporting techniques such as virtual reality, real-time simulation, path planning, human-computer interaction and so on. It is also an advanced research topic in cartology and geographic information system (GIS).This dissertation studies the key technologies in 3D virtual city construction with focus on the following four parts: massive terrain rendering, design and development of real-time navigation system with large-scale scene, path planning technique in 3D virtual scene and nearshore wave simulation in virtual seaside city.1. Massive terrain rendering.Related research about massive terrain rendering is discussed. Then a method based on pyramid structure is proposed to organize and dispatch geometric and texture data of massive terrain. Original data is pre-processed through hierarchy and block-division. Real-time rendering of massive terrain data is realized for only the visible data blocks are loaded into memory according to the view frustum and resolution level is selected according to the position and angle of the viewpoint and corn of normal.2. Real-time navigation system with large-scale sceneOn the basis of discussion on real-time navigation system with large-scale scene, related techniques including rendering acceleration technique, organization and management of virtual scene, rapid elimination and collision-avoidance are addressed. Afterwards, taking virtual campus as an example, real-time navigation system with large-scale scene is realized through VC and OpenGL programming from the viewpoint of integration of virtual reality, multi-media and GIS.3. Path planning technique in 3D virtual sceneRelated research about path planning technique is discussed. Based on analysis of path planning method in GIS and robotics, a new and fast automatic path planning algorithm elastic algorithm is proposed in view of the features of navigation in 3D virtual scene. First, basic path is generated using the projection matrix of the virtual scene; then, the path is optimized using elastic algorithm; finally the optimal path can be got. This algorithm has obvious advantage in solving problems such as collision-avoidance in complex scene and wide walkable region.4. Nearshore wave simulationRelated research about wave simulation technique is discussed. Aiming at the difficulty in nearshore wave simulation and requirement of seaside city virtual scene, a real-time simulation method of nearshore wave is put forward. The problem of wave curving and distortion in nearshore wave rendering is solved by using elliptic cosine functions to construct waveform and refraction simulation of nearshore wave is realized using deformable grids composed of wave rays and wave crests. Meanwhile, a rapid wave rays and wave crests generation algorithm fit for visual simulation is proposed and nearshore real-time simulation is successfully realized.更多还原